I’m working on a long paper right now with my colleague at Montclair State University, Adam Bell. (Update: here’s the paper.) The premise is this: In the past, metaphors came from hardware, which software emulated. In the future, metaphors will come from software, which hardware will emulate.
The first generation of digital audio workstations have taken their metaphors from multitrack tape, the mixing desk, keyboards, analog synths, printed scores, and so on. Even the purely digital audio waveforms and MIDI clips behave like segments of tape. Sometimes the metaphors are graphically abstracted, as they are in Pro Tools. Sometimes the graphics are more literal, as in Logic. Propellerhead Reason is the most skeuomorphic software of them all. The main image from the Propellerhead web site makes the intent of the designers crystal clear; the original analog synths dominate the image.
In Ableton Live, by contrast, hardware follows software. The metaphor behind Ableton’s Session View is a spreadsheet. Many of the instruments and effects have no hardware predecessor.